Indeed. Thank goodness I live in a world where resources are unlimited, everything is perfectly designed, and compromise is never required.
Compromise on user authentication is not only dangerous, it could be considered gross negligence today. In Court. Later. When sensitive data goes missing.
I'm picking a little on you because it's pretty easy to do this one right on most systems, and it's just that I don't know any modern operating systems that don't support individual logins.
Hell, we used to copy the /etc/passwd and /etc/shadow files by hand, but we never handed root to everyone. In the time for the search for sharing one password, that could have been automated on Unix. Windows too.
Sooooo... What kind of system is it? I'm curious. If it has the ability to do individual logins, I'll ask the standard question...
"If you don't have time/resources to do it right, where will you find time/resources to fix it later?"
User authentication is way too basic not to do right. FreeRADIUS and/or OpenLDAP and various other tools are quite literally, free. And can be run on a pair of complete junk servers.
I know 'cause I just decommissioned the company's original pair of Dell 1750s that did the job without fail for almost 10 years.
We have other compromises we want fixed, but logins per user and the ability to disable any account at a moment's notice parallels the real world since people leave, get fired, and die with regularity in anyplace big enough to need a password sharing system.
Think about it carefully. I've heard that excuse before and the systems always had to be reworked later after it was a lot more expensive in terms of man-hours and risk... since it required reconfiguration of Production 24/7 systems by the time it became "important enough".
Just trying to save you the mistakes I've seen before. Just like my Flight Instructors have done for me. It's not in a sprit of meanness, more in terms of "pay it forward".
A shared password list system will bite you in the butt. Hard. I've seen it happen. Just a warning.